1. Field of the Invention
The present invention relates to a base station apparatus, a mobile station apparatus, and a method for updating the radio communication parameters, and particularly to a base station apparatus of multiple access method in which a plurality of users make the communications at the same time by sharing a radio channel, a mobile station apparatus, and a method for updating the temporary radio communication parameters.
2. Description of the Related Art
As the multiple access methods in which a plurality of users make the communications by sharing a radio channel, a code division multiple access (CDMA), a time division multiple access (TDMA) and a frequency division multiple access (FDMA) are well known.
For example, in a communication system of code division multiple access method in which the same frequency band is shared among a plurality of communication waves, individual communication waves are distinguished by the spreading codes of random code series. As the spreading code is better in the detection characteristic (auto-correlation characteristic) and the identification characteristic (cross-correlation characteristic) between different spreading codes, the system efficiency is improved. Therefore, all the random combinations of codes determined by the series length are not employed, but the code series to attain the required characteristics are selectively employed. Accordingly, when the high system efficiency is required, the spreading code is limited and the assignable number of spreading codes is below the total number of simultaneous communication waves supposed for the system.
Particularly in the satellite downlink of a W-CDMA (Wideband CDMA) cellular system, the spreading code used is demanded to have the code orthogonality capable of reducing mutual interference between different spreading codes, in addition to the high detection characteristic and identification characteristic, to implement high quality communications even at low transmission power. Therefore, the assignable number of spreading codes is smaller than in the satellite uplink. This small number of spreading codes is repeatedly employed for effective use, but a different code for each cell is employed and superimposed to prevent radio interference between cells.
In the W-CDMA cellular system, the spreading code for actually spreading the user data in the broadband is called a channelization code, and the code for preventing radio interference between cells superimposed for each cell is called a scrambling code.
Each base station apparatus (hereinafter simply referred to as a base station) forming each cell of the W-CDMA cellular system reports the down scrambling code employed by its peripheral base station on the control channel so that a mobile station apparatus (hereinafter simply referred to as a mobile station) may detect the cell at high speed, and the mobile station makes the reception of the satellite downlink for the scrambling code notified on the control channel. Accordingly, when the down scrambling code is assigned to a certain base station, in order to enable the mobile station to make the reception on the satellite downlink of the base station, and then make the reception on another satellite downlink around the satellite downlink, it is required that the down scrambling code of the peripheral base station located around the base station is set on the control channel of the base station and reported to the mobile station belonging to the cell formed by the base station.
A technique in which the mobile station acquires the information of the base station and reports it to the base station to which the self station is connected, and the bases station update the information was described in JP2001-54158A.